import java.util.*;
import java.util.concurrent.locks.ReentrantLock;

/**
 * Created by rzd on 2017/4/2.
 */
public class Test {
    public static void main(String[] args) {
        HashMap<String,String> map=new HashMap<>();
        map.put("123", "456");
        Collections.sort(new ArrayList<Comparable>());
        System.out.println(16>>2);
        ReentrantLock lock;
        List<A> list = new ArrayList<>();
        show(list);
    }
    static void show( List<? super A> list)
    {

    }
}
class A
{
    static void show()
    {
        System.out.println(1);
    }
}

class B extends A{
    static void show()
    {
        System.out.println(2);
    }
}

